BlueLab pH Pen

What the Bluelab pH Pen Reads and How Accurately A pH reading that drifts is worse than no reading, because you feed on it. This pen covers 0.0 to 14.0 pH at 0.1 resolution and holds ±0.1 pH accuracy at 25°C. A double junction probe does the work. It also reads solution temperature across 0-50°C / 32-122°F and compensates automatically, so a cold reservoir at lights-on does not throw the number. The body is fully waterproof and the LCD is backlit for a dark room. A hold function freezes the reading so you can pull the probe out before squinting at it. One AAA battery, with a low-battery warning before it strands you mid-feed. Calibration and Probe Care on a Hydroponic pH Meter Calibrate against fresh 4.0 and 7.0 solution and keep the tip in storage solution between uses, never dry and never in plain water. A dried-out junction is what kills these pens, not the electronics. The pen tells you when a calibration takes, which is the difference between trusting a number and hoping. Here is the honest limit: the double junction probe is not replaceable, so when it finally goes, the pen goes with it. If you want a probe you can swap, step up to a Bluelab meter with a BNC connection. Also worth saying plainly, this reads solution, not root zone. Growers testing soil directly want the Bluelab Soil pH Pen instead. Key Features 0.0 to 14.0 pH at 0.1 resolution: Plus or minus 0.1 pH accuracy at 25C, tight enough to feed on. Automatic temperature compensation: Corrects the reading against solution temperature from 0-50C, so a cold reservoir does not skew the number. Fully waterproof body: Survives being dropped in the tank, which is where most pens end their careers. Backlit LCD with hold function: Freezes the reading so you can lift the probe and read it in a dark flower room. Successful calibration indicator: Confirms the calibration took instead of leaving you guessing whether the pen is telling the truth. Technical Specifications Specification Value Measures pH and temperature pH Range 0.0 to 14.0 pH pH Resolution 0.1 pH pH Accuracy ±0.1 pH @ 25°C Temperature Range 0-50°C / 32-122°F Temperature Resolution 1°C / 1°F Probe Double junction (not replaceable) Display Backlit LCD, selectable °C / °F Water Resistance Fully waterproof Battery 1 x AAA alkaline Other Functions Hold, auto-off, low battery warning Guarantee 12 months